The invention relates in particular to flexible curtains for goods-handling doors. Goods-handling doors are installed on buildings such as factories and warehouses in which there is a need for considerable traffic between the inside and the outside. The purpose of such doors is to provide a heat screen, i.e. to reduce heat exchange between the inside and the outside while avoiding impeding the passage of goods-handling vehicles. For these reasons, doors of this type are fast-acting, both when opening in order to provide passage for users substantially instantaneously, and when closing in order to limit as much as possible the time during which inside and outside masses of air come into contact. For structural reasons, the necessity of fast action has given rise to the development of lifting curtain doors which are made of light material, typically cloth or plastified cloth or plastic film.
Given the buildings in which such doors are usually installed (factories, warehouses, etc.) and regardless of the way in which the curtain is raised (e.g. by being wound around a shaft running over the opening, or by being folded concertina-like by mean of straps which are wound around a shaft running over the opening, or by being wound around a bar fixed to the bottom edge of the curtain, likewise by means of straps which in turn are wound around a shaft running over the opening) the curtains of such doors are generally large in size and it is important to stiffen them at regular intervals by means of horizontal reinforcing bars. It is conventional to fix such reinforcing bars to a flexible curtain by providing horizontal sheaths at regular intervals along the curtain with the reinforcing bars being inserted therein.
Given also the fairly high traffic density which such doors pass and the need to prevent collisions which could arise between two vehicles arriving simultaneously from opposite sides of an opaque curtain, windows are generally provided in the curtains of such doors and extend over a portion of their height, said windows being closed with transparent flexible plastic material.
From the above, it will easily be understood that using a roll of plastified cloth of given width to fabricate a curtain for a goods-handling door extending over several meters in each direction and including horizontal sheaths for receiving reinforcing bars and optionally including windows is a relatively complex operation.
Heretofore the curtains of goods-handling doors have been fabricated by craft methods. Thus, in order to make a curtain of height H and width W, a roll of plastified cloth of standard width (advantageously the widest width avilable on the market, which at present is 1.40 m) is cut into as many strips of length W as are required to fill the height H with widths of said plastified cloth, plus a margin. Two of these strips are then aligned with an overlapping margin of given width on an oblong table over which there is a device for welding (or sewing, or equivalent) capable of moving parallel to the longitudinal axis of said table. A shoe of the welding device is then placed over the overlap margin and the device is moved as often as necessary in order to weld together the two strips over their entire length. The operation is then repeated to weld another strip to the preceding strips, and so on until an entire curtain has been assembled. Once the curtain has been assembled, plastified cloth tapes are fastened to one of its faces at regular intervals parallel to its width by successively welding their longitudinal edges so as to form the sheaths for receiving the reinforcing bars. Once the curtain is provided with these sheaths, windows are optionally cut out between some of them and then closed by welding pieces of flexible transparent material therein. Naturally, these pieces are cut out to have greater areas than the windows by an amount sufficient to leave a peripheral overlap margin for welding purposes.
Heretofore, all stages of such fabrication have been performed manually, in particular the strips have been positioned manually relative to one another, they have been kept in place manually during welding, the windows have been cut out manually, and the transparent parts for closing the windows have been welded manually into place. Further, as described above, the strips have been positioned successively, i.e. there have never been more than two pieces of curtain which are being positioned relative to each other (either two strips at the beginning of curtain assembly, or subsequently one strip and the assembly of strips which have already been welded together). This fabrication method suffers from several major drawbacks, in particular requiring considerable manpower and considerable time, to which must subsequently be added the time required for inserting the reinforcing bars into each of the sheaths. Furthermore, curtains obtained by performing this method can be seen to be constituted by strips which are only approximately squared up and if they have windows, they have weak zones running along the vertical welds of the transparent parts, i.e. along the welds which extend perpendicularly to the winding or folding axis of the curtain.
The aim of the present invention is to remedy these various constitutional defects and drawbacks. It comprises apparatus for implementing a fabrication method which is both rapid and economical in manpower for fabricating flexible curtains for goods-handling doors whose strips and sheaths are accurately squared up prior to welding and which optionally include large area transparent surfaces while avoiding weak zones, in particular along intermediate vertical welds, while costing less than a prior art curtain.